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Unanswered: about catalog database

Hi all, i have some questions can make sure correct answer , can someone help me ?

Which of the following is the most appropriate reason to consider revoking the SELECT privilege on the catalog tables from PUBLIC after creating a database?

A. To prevent users from creating tables without proper authority.
B. Some system catalogs record user data in some columns, and this data may be confidential.
C. To prevent users from viewing passwords for other DB2 userids that DB2 stores in the catalog tables.
D. Some catalog tables are large, so preventing users from viewing them is a
good way to keep users from submitting long-running queries against the catalogs.

DB2 does not store user credentials (id/password) in any catalog table.
Is it mean this answer is B ?

Cataloging a remote database is:
a) Performed on a PC or UNIX machine to identify the server the DB2 data base manager is on.
b) Performed on a PC or UNIX machine to identify the DB2 database to use rs and applications.
c) Never performed in DB2, as only one database per node is allowed, so cataloging a node automatically catalogs the database at that node.
d) Performed on a PC or UNIX machine to open the catalogs in the DB2 database and present a user with a list of all accessible tables in that database.
which one is correct answer ? D or B ?

I suggest that you (the OP) start to give us your reasonings on the separate points. I don't see the benefit of you just asking and don't thinking for yourself. Anyway...

First question:
A is obviously wrong. The creation of database objects is controlled via other privileges and not by revoking SELECT privileges on catalog views.
B is possible and probably the correct answer. For example, if you have a column SALARY in some table showing the salary of all employees and if you collect statistics on that table, then the catalog will contain the highest (and lowest) values in that column. Thus, you could derive the highest salary - which may be confidential and not for your eyes if it is not your own salary.
C is not correct - you already gave the answer (no user credentials in the catalog)
D may be possible, too. You could write queries that put load on the catalog tables and, thus, incur locking. But I don't think this is a problem.

2nd question:
A is not correct. The CATALOG NODE command would be used for that.
B is correct.
C is not correct because there may be multiple databases in a DB2 LUW instance.
D is not correct; CATALOG DB does not access or "open" the database - it just creates an entry in the local database directory